This invention relates to an apparatus for data transfer with a rotating data storage disk such as, typically, a flexible magnetic disk commonly known as floppy disk and, more particularly, to a flexible magnetic disk drive suitable for connection as a peripheral to a personal computer via a universal serial bus (USB) interface. Still more particularly, the invention concerns how to reduce the maximum current requirement of such a disk drive, specifically dealing with the reduction of current consumption by a pilot lamp that is customarily affixed to the front face of the disk drive in order to warn the user that the disk is being accessed.
There recently have been introduced to the market the personal computers that have what is called a universal serial bus (USB) port for connection to a set of peripherals via serial USB interfaces. A plurality of peripherals, each with a USB interface, may be connected to what is termed a USB hub via separate USB cables and thence to the USB port of the computer via a single USB cable. USB connections are generally acknowledged to greatly enhance the utility and versatility of computer systems.
There has, however, been a problem left unsolved in connection with the USB interfacing of personal computers and peripherals. USBs are capable of carrying a current of no more than 500 milliamperes, which means that the maximum current requirement of each computer peripheral should not exceed that limit. Difficulties have been experienced in de signing magnetic disk drives, among other peripherals, so as to meet this requirement. The difficulties arise for the most part from the large current consumptions of the disk drive motor and the stepper motor for transducer positioning, both incorporated in a floppy disk drive to enable the transducers to access the individual storage locations on the disk for reading or writing.
Flexible magnetic disk drives have, moreover, a pilot lamp on the front face of their casing that glows continuously when a disk is loaded in the disk drive, being driven by the disk drive motor, and being read or written upon, as well as when the transducers are being transported by the stepper motor for track seeking. This pilot lamp represents another source of current consumption, adding substantially to current consumptions by the disk drive motor and the transducer positioning motor. The total current requirement of the disk drive maximizes when both disk drive motor and transducer positioning motor are in rotation with the concurrent continuous glowing of the pilot lamp. The present invention is based upon the discovery that, although the current consumptions of the motors may not be reducible, or at least not easily so, that of the pilot lamp is.
The present invention seeks therefore to lower the maximum current requirement of a disk drive through reduction of the current consumption of the pilot lamp, or equivalent indicator means, without any substantial impairment of the intended functions of the indicator means.
Briefly, the invention may be summarized as a rotating disk data storage apparatus having a reduced maximum current requirement, comprising a positioning motor for moving a transducer or a pair of transducers across track turns on a disk, and a motor driver circuit for controllably driving the positioning motor by causing energization thereof with a periodically varying motor current, each period of the motor current being notionally divisible into a first and a second part such that the motor current is less in magnitude in the first part than in the second. Also included are an indicator such as a pilot lamp for indicating that the positioning motor is in operation, and an indicator control circuit for permitting the indicator to be energized with an indicator current only during the first part of each period of the motor current energizing the positioning motor.
Thus the indicator lamp blinks, instead of glowing continuously as has been the case heretofore, being lit up only during the first part of each period of the motor current when the motor current is less. Consequently, the peak of the sum of the motor current and the indicator current during the first part of the motor current period can be made no more than the peak of the motor current alone during the second part of the motor current period. The current consumption of the glowing lamp does not increase the total current consumption of the complete apparatus when both positioning motor and disk drive motor are in operation; in other words, the maximum current consumption of the apparatus remains the same whether the lamp is on or off.
In preferred embodiments of the invention to be disclosed herein, the apparatus takes the form of a flexible magnetic disk drive, in which the positioning motor is a stepper motor which rotates by discrete increments in response to stepping pulses generated both externally and internally of the disk drive. The present invention is equally well applicable whether the stepper motor is driven by successively exciting one or two phase windings thereof or by alternately exciting one and two phase windings, both according to the prior art. The lamp control circuit for making the pilot lamp glow intermittently takes different forms depending upon which excitation method is employed.
In cases where the stepper motor is driven by the one-or two-phase excitation method, the lamp control circuit incorporates means such as a timer responsive to each stepping pulse for providing a lamp control signal indicative of two divisions of each stepping pulse period, which are equivalent to the first and second parts of each motor current period. The lamp control signal can therefore be used directly for causing the lamp to be energized during the first division of each stepping pulse period.
If the one-two-phase excitation method is employed, on the other hand, then the successive stepping pulse cycles alternate between the cycle during which one phase of the stepper motor is energized and the cycle during which two phases of the stepper motor are energized simultaneously. The current consumption of the stepper motor is of course less during the one-phase excitation cycles than during the two-phase excitation cycles. The lamp control circuit may therefore discriminate between the one- and two-phase excitation cycles of the stepping pulses, causing the pilot lamp to be energized only during the one-phase excitation cycles.
In either case the invention makes utmost use of preexisting parts of the disk drive. No major alteration of such preexisting parts is needed for reduction of the maximum current requirement of the disk drive according to the invention.
The above and other objects, features and advantages of this invention and the manner of achieving them will become more apparent, and the invention itself will best be understood, from a study of the following description and attached claims, with reference had to the accompanying drawings showing the preferred embodiments of the invention.